On the first day of 1992, by hitting on an idea, I started to move toward one direction. Since all the leading scholars and industries had already made considerable efforts to reach the present status at that time, it should not be possible to increase the energy density of capacitors to 20 times under the same conditions. For performance of any one thing such as an engine or generator to be improved to 20 times must need a great effort.... at this stage, I hit upon one important point.

Can't we take away the two requirements of "under the same condition" and "any one thing"? The capacitors had to be low resistance. It needed to be kept low because any internal resistance will result in a loss of electricity and decrease in its charging/discharging efficiency. By removing this condition of low internal resistance, there should be a possibility of obtaining higher energy density.

The most important point to overcome was that the energy density of capacitors might be difficult to increase by 20 times. However, if you have two individual factors that can be improved 4 and 5 times respectively, then you could get 20 times improvement in total. By sacrificing internal resistance the capacitor energy density could be improved up to 5 times, and by surmounting deficient capacitor utilization by means of electronic circuits, another 4 times improvement could be obtained. This was the concept of ECaSS® (used to be called ECS) when it started.

As you may expect, the ECaSS® concept requires various kinds of knowledge across many scientific fields. Fortunately, we had some experience in electronics and electrical engineering, physics, chemistry, nuclear and computer science. Using SPICE, an analog circuit simulator, we built and tested 2000 cells of 4 V, 4000 F capacitors in my computer, resulting in almost the same performance of today. However, it took long time to actually build and manufacture a real one. Figure 1 is a picture of an experimental ECaSS® set to light a 50 W headlamp for 25 minutes using two capacitor modules (12.5Wh each) in the center

You can easily see through manufacturing that if internal resistance is allowed to increase, the energy density can be increased. The carbon electrode can be made thicker, and the collector and lead-out wires made to be thinner. Though, any electric engineer can point out that "loss must be increased with larger resistance".

The fact is that larger resistance increases the loss when charged with the same current. However, with a capacitor that has 10 times larger resistance with 1/10 current, or by spending 10 times the charging time, the total amount of loss is the same. As shown in Figure 2, the charging/discharging efficiency of capacitor is not determined by the absolute value of R but the ratio of RC/t where t is the charging time of capacitor. [1] Right after the debut of this principle, there was a lot of discouraging advice that such a lossy capacitor cannot be used practically, however, it is an ECaSS® feature to optimize the internal resistance of the capacitor according to charge/discharge requirements.

When charged from constant voltage sources such as batteries, the charging efficiency of any capacitor will settle to 50% regardless of their internal resistance. [1] This phenomenon is understood well but not regarded seriously because there are no significant problems as far as applications limited to small ones such as toys or memory backup.

Charge/discharge efficiency and depth of capacitors can be greatly improved, by usually more than double by utilizing charging control current source circuits, specially designed switching converters or bank switching methods.

On the other hand, as the rated voltage of EDLC is usually low at 2.5 volts, the cells must be connected serially. Meanwhile, a problem occurs where the applied voltage is not equally distributed.

If the total operating voltage of serially connected capacitors is reduced to 70%, the storable energy will be decreased to 49%. Since 70% is not safe margin for average capacitor products, this is the point to improve for ECaSS® electronics. For an entire basic configuration of ECaSS as shown in Figure 3, there are small circuits called "parallel monitors" that initialize all the capacitors to the same starting voltage. [1]